Discovered by Giovanni Domenico Cassini Date of Discovery 1684 Distance from Saturn 294,660 km Radius 535.6 × 528.2 × 525.8 km Mass 6.27 × 10^23 g Orbital Eccentricity 0.00000 Orbital Inclination 1.86° Orbital Period 1.887802160 days Rotational Period Synchronous Density (gm/cm3) 1.21
Like Dione and Rhea, this satellite is heavily cratered and almost completely composed of water ice. The largest crater, named Odysseus, seems to be partially smoothed out, indicating a period of the moon's history when it partially liquefied. Tethys differs somewhat from the other two in that its surface is also heavily marked by cracks and faults. It is believed that these were caused by the surface freezing before the core. One of these cracks, called Ithaca Chasma, is approximately 65 km wide and covers almost 3/4 of the moon's circumference.
Tethys shares its orbit with two Trojan moons, or bodies sharing its orbit at the Lagrange points. Telesto precedes Tethys by 60°, and Calypso trails 60° behind. If you plan on going, bring a coat because the surface temperature is -187° C.
Sources: NASA.gov space.com